In many situations, multiple user equipments (UEs) may be co-located within a small area. For example, in a vehicle, the vehicle itself may have a first UE, and various passengers within the vehicle may have a plurality of other UEs.
A first UE, for example a vehicle's UE, may have a better data connection with a network than portable user equipments. For example, the vehicle's UE may have a roof mounted antenna, which allows for better signal reception than the vehicle's passengers' UEs.
Further, in many situations, each of the UEs in the small area may have a separate or different IMS/Session Initiation Protocol (SIP) service provider. Such UEs may also each have a different Home Public Land Mobile Network (HPLMN) and may be associated with different Visited or Registered Public Land Mobile Network (VPLMN or RPLMN, respectively).